The present invention relates generally to apparatus that allows access to the vascular system of a human (or other animal), particularly for the high-volume fluid flow required in hemodialysis, plasmapheresis and other fluid exchange therapies. More particularly, the present invention relates to a septum-less, subcutaneously-implantable access device of single or dual-lumen construct, and mating needle apparatus.
There exists a class of devices for accessing fluid spaces and vessels within a human (or animal) body that are generally referred to as xe2x80x9cportsxe2x80x9d. Herein, xe2x80x9cvesselxe2x80x9d is defined as any conduit carrying a fluid within the patient""s body. These prior art port devices generally comprise a chamber having an access opening sealed by means of a septum and having an egress from a second location leading to a catheter which is disposed within a fluid space or vessel. The septum allows a hollow needle (or xe2x80x9ccannulaxe2x80x9d) to pass into the port""s chamber, but then closes when the needle is removed, thereby preventing fluid leakage from within the bodily fluid space or vessel and also preventing anything from entering or exiting the port""s chamber. These port devices are usually implantable below the skin so as to prevent infection, other contamination and mishandling.
Prior art ports are designed for relatively infrequent use, perhaps once a week, and, importantly, for fluid flow rates of 50 milliliters per minute or less, as is common during chemotherapeutic treatment. Modification of these prior art port devices for hemodialysis, plasmapheresis and other fluid exchange therapies, which require much greater flow rates, by simply enlarging the device components, poses several serious drawbacks that effectively limit use in such high-volume applications.
First, the prior art port""s septum degrades quickly due to the larger gauge needles necessary to accommodate the higher flow rates required in hemodialysis. Repeated puncturing of the septum by these large needles produces numerous free-floating septum fragments that can find their way into the patient""s circulatory system. Accordingly, the useful life of the port device is substantially shortened, thereby defeating one of the purposes of using an implantable subcutaneous access device.
Second, the prior art port""s flow path has several stagnation points where clots may form, and the port is also not completely flushable or easily cleaned, thereby providing breeding grounds for infection, once contaminated, or a build-up of material which may adversely affect function.
Third, the prior art port""s flow path is not streamlined and contains flow path obstructions, sharp corners, and abrupt changes in flow area and flow direction. This tends to increase the shear stress and turbulences experienced by blood flowing through the port device due to the significantly higher flow rates required in hemodialysis, thereby increasing erythrocyte damage and platelet activation. Also, the prior art port""s tortuous flow path increases the flow path resistance and the pressure drop through the port device; such effects can increase air release and foaming, thereby causing the dialysis machine""s safety alarms to activate.
A general limitation in all relevant prior art port devices is the lack of a streamlined flow path. Without such streamlining, stagnant volumes exist where clots may form and shear stress is higher, tending towards erythrocytic damage. Such locations cannot be flushed or easily cleaned. Blood residue remaining in the devices after flushing may clot and may provide breeding grounds for infection, once contaminated. In addition, pressure drops and abrupt flow direction changes may damage blood components.
The present invention is also useful for other liquid or fluid (including gases) transfer purposes into and out of human and animal bodies, including the transfer of externally-prepared solutions for cleaning, flushing, dialysis, chemical agent delivery, transfusions, blood donation, insufflation, wound drainage, etc.
Accordingly, it is a principal object of this invention to overcome the above-illustrated inadequacies and problems of extant devices by providing a totally implantable access means suitable for repeated use in applications (e.g., hemodialysis) with blood flow rates of 250 milliliters per minute or more, yet with low pressure drops along the flow path.
It is another principal object of the present invention to optimize fluid flow, in hemodialysis particularly, and in other applications referred to generally, above.
It is another object of this invention to provide a substantially laminar flowstream.
It is yet another object of this invention to minimize flow discontinuities and to substantially match the internal diameters of the injecting needle (or cannula) and the receiving catheter, and a related object is to bring the exit end of the needle (or cannula) and the entrance end of the catheter into close proximity.
It is a further object of this invention to provide access means where the flow path is streamlined and provides substantially no stagnation points and no flow discontinuities, and also to provide an apparatus where the entire flowstream is flushable.
It is a further object of the present invention to minimize internal fluid collection zones or stagnant volumes in such an access device.
It is a still further object of this invention to have lower clotting, stenosis and infection rates than with synthetic grafts.
It is yet another object of this invention to have lower infection and lumen clotting rates than with percutaneous catheters.
It is a still further object of this invention to provide apparatus suitable for single and dual-lumen catheter systems.
It is yet another object of this invention to provide an access device that is less painful during needle (or cannula) insertion and more accommodating during dialysis for the patient.
It is a further object of the present invention to minimize irritation and other adverse effects associated with intermittent skin punctures over a course of days, months or years of repetitive subcutaneous access.
It is a further object of this invention to secure the needle (or cannula) within the access device during the dialysis session.
It is a further object of the present invention to enhance the access device so as to more effectively lock in a needle (or cannula) to the access device in order to avoid inadvertent separation, yet allow ease of deliberate release of the needle (or cannula).
It is a further object of the present invention to provide ease of manufacture and assembly of such an access device consistent with enhanced locking.
A further object of the present invention is to establish economy of the lock devices for disposability.
It is a further object of the present invention to provide enhanced needle (or cannula) and obturator handling external to a patient via hub devices coordinated with the structure and functions of the locking devices.
It is another object of the present invention, when using dual-lumen catheters, to secure both needles (or cannulas) to each other.
And another object of the present invention is to provide improved needle (or cannula) and obturator assemblies.
It is also an object of the present invention to accommodate multiples of the foregoing objects together.
The foregoing objects are met by a single subcutaneously-implantable device for accessing a vessel within a patient""s body, or a ganged pair of such devices or separate such devices, each device including (a) access guidance means having an entrance and a passageway for receiving a needle (or cannula) and accommodating a locking means for the needle (or cannula), (b) flexible locking means, (c) needle guidance means of sufficient hardness to prevent scoring or chipping, (d) valve means for allowing access to a vessel when a needle (or cannula) is inserted into the device and preventing fluid flow through the device when the needle (or cannula) is withdrawn from the device, the valve means having a closable passageway that accepts an inserted needle (or cannula) and comprising an access portion, a sealing portion, and a distal portion; (e) a catheter attachment having a closable passageway with seating means disposed therein, and (f) a shell capable of enclosing these elements.
A resilient elastomeric means for producing a contact sealing pressure is arranged around the sealing portion of the valve means. This resilient elastomeric means includes, in a preferred embodiment, a cylindrical band made of an elastomeric material that provides forces on the sealing portion and is located outside the fluid path. The sealing portion ordinarily prohibits fluids from passing through the seal. But when a mechanical device (e.g., a needle or cannula assembly) is inserted percutaneously, and guided to the valve""s access portion by the access guidance means, the mechanical device (e.g., the needle or cannula assembly) engages the needle guidance means disposed within the access portion of the valve with sufficient axial force to overcome the radial force exerted on the sealing portion by the resilient means for sealing. It is important to note that the needle (or cannula) assembly forces the guidance means, and the guidance means pushes the sealing portion open. The needle (or cannula) assembly, actually an obturator which is part of the needle (or cannula) assembly in a preferred embodiment, then enters the opened sealing means without the point of the obturator puncturing or cutting the sealing means. The needle guidance means itself opens a slit to allow the needle (or cannula) assembly to enter and then to slip through the sealing means. So in this fashion the needle (or cannula) assembly passes through the valve until the needle (or cannula) assembly engages the catheter attachment seating means. This operation provides access through the valve to the valve""s distal portion and, ultimately, to the vessel lumen, as the distal portion of the catheter (that is attached to the access device via the catheter attachment) extends into a vessel lumen.
An advantage of the present invention is found by minimizing the spacing between the end of the needle (or cannula) and the beginning of the catheter, and by smoothly fairing the internal surfaces of the short connecting or transition passageway to the interior surfaces of the needle (or cannula) and the catheter. If there are disparate internal diameters, the short connecting transition passageway smoothly and uniformly accommodates the internal diameters. This arrangement provides a flow path with minimum flow discontinuities and a path that is easily flushed.
The catheter may be flexibly attached to the surrounding tissue supporting the catheter, but the flexibility allows the access device""s position to move relative to the surrounding tissue. A strain relief assembly may also be provided at the catheter attaching end of the access device so as to relieve tension on the catheter attachment to the access device, whereby to prevent catheter kinking. Edges of the strain relief structure can be sutured or stapled to adjacent tissue, and the strain relief wrap can in turn hold other portions of the access device.
The access device may be flexibly anchored to the surrounding tissue. In a preferred embodiment, such anchor means are attached to the access device so as to allow the needle (or cannula) entrance of the access device to be rotated, preferably by as much as 50 degrees relative to the anchor means in at least two directions. This, together with the normal movement of the skin, allows the needle (or cannula) assembly to enter the skin at a location on the skin that is healed, or at least a skin location that has had ample time to heal. This ability to access larger areas of skin for inserting the needle (or cannula) assembly is a significant advantage over relatively fixed ports.
The resilient means for sealing is arranged and constructed so as to close the valve""s potential lumen such that the longitudinal transition profile of the valve""s access portion forms a particular shape. The shape of the access portion allows for the generally conical point of the needle (or cannula) assembly""s obturator to open or push apart the access portion, and the slit in the sealing portion, with a wedging action as the obturator""s point is pushed through the seal. The axial point-pushing force overcomes the radial biasing force exerted by the resilient means for sealing, and the internal stresses of the sealing portion, as the obturator""s point enters the sealing portion, without cutting the valve material. Because no cutting occurs, no particles of valve material are generated, as is common with septums in ports now in use. Furthermore, the number of penetration cycles to failure in the present invention is significantly higher than with septum ports, as negligible damage occurs during needle (or cannula) penetration.
The flow path transitions between the needle (or cannula) lumen, the short connecting passage in the access device, and the catheter lumen are arranged and constructed so as to provide for maximum smoothness and continuous flow paths without abrupt changes in flow diameter and only gentle changes in flow direction. All narrowing and broadening of the flow path is gradual, with angles of preferably 25 degrees or less.
The invention also provides for a hollow needle (or cannula) apparatus with an outside diameter that matingly corresponds to the entry passageway of the access device, and an obturator that is inserted into the needle (or cannula) lumen, filling the lumen, and which has a tip portion that extends beyond the needle (or cannula). This needle/obturator combination provides a needle (or cannula) assembly with a pointed end, and an outer surface having smooth transitions, which are formed to puncture tissue easily and to open the valve without damaging it. The hollow needle (or cannula) is preferably made of metal so that the needle wall may be formed as thin as possible considering the stresses on the needle. This is important, since the larger the internal diameter of the needle (or cannula), the lower is the flow resistance. The lowest flow resistance consistent with the physical constraints and needs of the patient and the function being performed, especially in the high flow rate hemodialysis field, is an important goal of the present invention and a major advantage of the present invention.
The flexible lock preferably comprises a resilient plug (preferably made of a medical quality elastomer) surrounding an inserted hollow metal needle (or cannula), but containing rigid internal blades or strips (preferably made of a super hard material such as a hard ceramic or hardened metal, e.g. titanium nitride) that extend radially in locking use and are configured and arranged to inscribe the outer needle (or cannula) surface and bear on it with a high reaction force. When an inadvertent axial pull on the needle (or cannula) from outside, or the push of a muscular contraction from within, places an expelling force on the needle (or cannula), the beginning of movement increases the locking effect. The blades or strips have inner edges that form one or more teeth of pointed or blunt ends, such teeth having shallow clearance angles with respect to the passage axis. The blades have outer edges that are locked in geometrically by a tapered inner surface of the shell. Deliberate removal can be done by rotating and/or wiggling (spiral or a combination of axial/rotational movements) of the needle (or cannula) so that the orientation of the blades shifts, from essentially radial to essentially chordal or non-radial alignment relative to the access device""s internal passage axis. When the plug and blades are disposed non-radially, the needle (or cannula) can be withdrawn easily. The rotation or the like is then relaxed (after complete removal of the needle or cannula) and the blades are restored to radial alignment by the elasticity of the plug. When the needle (or cannula) is thereafter re-inserted into the access device, typically one or more days later, the entering needle (or cannula) passes through the inner edges of the blades.
Generally there is a full withdrawal of a needle (or cannula) or a full insertion; but partial insertion and/or partial withdrawal can also be accommodated. The resilient plug body is set radially apart from the needle (or cannula) surface so as to avoid shedding or uneven friction due to thermal conditions or other sources of expansion/contraction of the flexible plug (e.g., made of silicone rubber). The flexible plug material is preferably cast in a mold about the aligned (radial) blades. Holes or the equivalent are preferably provided in the blades so that the flexible material on both sides of each blade is bridged via such holes or other means, and the blades are securely aligned therein, radially and with inner and outer edges of the blades extending beyond inner and outer plug surfaces. Generally, there is a low-axial-direction friction meeting of the blade outer edges and the tapered (frusto-conical) shell inner surface. A ceramic shell with a smooth-finish, inner-tapered surface meets this criterion very well. Similarly, the blade inner edges slide along the needle (or cannula) outer surface with low friction. The hardness of all such surfaces, and the rigidity and dimensional stability of blades, needle (or cannula) and shell, are related to the above features and also important per se.
The valve, in a preferred embodiment, may include a plug of sealing material with a slit cut in the center, and with a spring loading means holding the slit closed, so as to block the internal passage of the access device when the needle (or cannula) is withdrawn and yet is readily opened as the leading portion of the needle (or cannula) assembly (i.e., the obturator) is inserted, without damage, as described above. Similar valves can be used with more than one slit opening and closing as described above. In any such design, it is preferable to have automatic, spring-loaded closing when the needle (or cannula) is withdrawn, and easy opening as a needle (or cannula) assembly, or the like, is inserted through the access device""s internal passage, so as to maintain contact sealing stress when the valve is closed. The present invention causes no cutting due to the manner of opening the seal described above.
Ease of use and product reliability are also accommodated by the features discussed above and below.
The invention also includes an extracorporeal needle (or cannula) assembly hub structure, or pair of such structures, usable in combination with the implantable subcutaneous access device(s) for straight needle (or cannula) alignment, and an aligned cutter and stiffener (a separate element or integrated with the needle or cannula) that has to penetrate the skin, find the entrance to the inner passage of the subcutaneous access device and pass through it to a lock-in site therein without coring the skin. The hub structure preferably has a Y-connection of three internal paths: (a) external fluid passage, (b) passage to the needle or cannula, and (c) a cannula/cutter access leg, all cooperating with shallow bend angles and gradual curvatures at the Y-intersection in the fluid path, and straight line access to the needle (or cannula) assembly locking device, as consistent with practical and economic mass production, while achieving a benign flow path which does not damage cellular blood components and meets previously stated criteria for the blood path.
The needle (or cannula) is initially inserted through the hub structure (or comes pre-assembled with it) and has an internal obturator with a point that passes out of the needle (or cannula) distal end for penetrating skin and subcutaneous tissue and serving as an aid to finding the subcutaneous entrance to the access and lock device. The obturator point is faceted so that its cutting is done along meeting-line edges of the facets. However, when the obturator point has cutting edges that extend from the center towards the outer surface of the obturator, as the cutting edges extend to the outer surface of the obturator, the edges are preferably softened or dulled so that the obturator does not cut, score or otherwise mar the internal wall of the passage or the interiors of the locking and sealing components of the access device which form part of the passage. The obturator edges are softened in a preferred embodiment by facets, but in a larger number of facets, set at shallower angles, than the facets at the obturator""s point. In yet another preferred embodiment, the facets are concave rather than flat, where the intersection of the facets provides a sharper edge. The section of the obturator with the dulled edges blends into a beveled end of the needle (or cannula).
Once the needle (or cannula) assembly is fully inserted in the access device, and locked and sealed in place, the obturator can be withdrawn from the needle (or cannula) so as to leave a smooth flow path beginning in the needle (or cannula) hub structure and continuing therein to a smooth blending with the proximal needle (or cannula) region of the hub structure, and continuing through the full length of the needle (or cannula) to emerge at the distal end and, in turn, blend smoothly with the access device""s internal transition passage, and then into the implantable catheter within the patient.
The access device of the present invention is suitable for both single-needle and standard (i.e., dual-needle) hemodialysis, plasmapheresis and fluid exchange therapy applications. For standard applications, which require two flow paths, the access device""s housing may be arranged and constructed to engage two needle (or cannula) hub assemblies, as described above, and include dual-lumen through-passageways. When two needles and needle hubs are used, a bar may be provided that engages each needle hub, thereby locking both needles to each other to preclude inadvertent disconnection of only one needle, thereby enhancing patient safety. In another preferred embodiment, the two needle hubs are prevented from moving laterally with respect to each other.
It is important to note that a primary object of this invention is to provide an implantable, subcutaneous access device suitable for applications requiring flow rates of 250 milliliters per minute or greater, with low pressure drops along a streamlined flow path having substantially no stagnation points or other flow discontinuities. Low pressure drops and substantial elimination of stagnation points are achieved by having maximum internal diameters of the flow path (and, therefore, thinnest needle or cannula walls), smooth transition points where different elements of the access device abut (e.g., the cannula-transition element-catheter interface) and by having all changes in lumen diameter be of a gradual nature and having a straight, or nearly straight, flow path without sharp curves or objects protruding into the flow path, and no dead volume.
As indicated above, because such large flow rates are desired with low resistance, it is preferable to have the largest needle (or cannula) outside diameter that patients will accept. Accordingly, rigidity of the puncture needle (or cannula) is desired. A rigid needle (or cannula) allows a greater inner lumen diameter per outer component diameter (i.e., thinner walls) than does a flexible tube. This is important, because it allows the needle (or cannula) to have as small a cross-sectional diameter as possible, thereby lessening the trauma on the patient""s puncture site, yet still being capable of handling large flow rates. Flexible tubes require much higher outer diameter-to-inner diameter aspect ratios in order to prevent kinking or tube collapse. Thus, to accommodate the substantial bloodflows common during hemodialysis, a much larger outer diameter needle (or cannula) would be required if flexible materials were used. Also, a rigid needle (or cannula) allows a greater force to be transmitted to open the seal valve by overcoming the resistance provided by the biasing means. Thus, a greater contact sealing force can be employed where the needle (or cannula) is rigid, resulting in a more robust, reliable, and fault-tolerant valve seal.
Further, the lack of sharp angles or bends in the flow path is much less injurious to fragile hematocytes. Since the flow path from needle (or cannula) to catheter, or vice versa, is substantially straight, the fluid turbulence is minimized, the shear stresses are lessened, and the flow directional changes are minimized, resulting in less erythrocyte damage and a lowered tendency toward platelet activation.
A medically-acceptable, water-based lubricant can also be used on the needle (or cannula) exterior, as an enhanced lifespan has been observed when such a lubricant is used. Also, a lubricated needle (or cannula) will generally penetrate the skin with less pain to the patient.
The invention further provides a needle (or cannula) and obturator assembly for access to entrance lumens in an access device disposed subcutaneously in a body of a mammal, for transfer of fluid into and/or out of the mammal body. The needle (or cannula) and obturator assembly comprises a first needle (or cannula) and obturator unit for insertion through a skin portion of the mammal body and into a first of the lumens of the access device, a second needle (or cannula) and obturator unit for insertion through the skin portion of the mammal body and into a second of the lumens of the access device, and hub structure for supporting the first and second needle (or cannula) and obturator units in fixed, spaced-apart positions relative to each other after complete insertion of the first and second needle (or cannula) and obturator units in the respective lumens. The first and second obturators are withdrawable from their respective needles (or cannulas) to open first and second passageways in the respective needles (or cannulas) for the transfer of fluid into and/or out of the access device.
The invention further provides a method for accessing an access device disposed subcutaneously in a body of a mammal and having entrance lumens for transfer of fluid into and out of the mammal body, the method comprising the steps (1) providing a needle (or cannula) and obturator assembly, the needle (or cannula) and obturator assembly comprising a first needle (or cannula) and obturator unit for insertion through a skin portion of the mammal body and into a first of the lumens of the access device, a second needle (or cannula) and obturator unit for insertion through the skin portion of the mammal body and into a second of the lumens of the access device, and hub structure for supporting the first and second needle (or cannula) and obturator units, the hub structure comprising a hub body having the first and second needle (or cannula) and obturator units fixed therein, (2) advancing the first and second needle (or cannula) and obturator units substantially simultaneously through the skin portion and into the first and second lumens, respectively, and (3) withdrawing obturator portions of the first and second needle (or cannula) and obturator units to provide passageways between the access device and the hub body for flow of fluid therebetween.
The invention still further provides a method for accessing an access device disposed subcutaneously in a body of a mammal and having entrance lumens for transfer of fluid into and out of the mammal body, the method comprising the steps of (1) providing a needle (or cannula) and obturator assembly, the needle (or cannula) and obturator assembly comprising a first needle (or cannula) and obturator unit for insertion through a skin portion of the mammal body and into a first of the lumens of the access device, a second needle (or cannula) and obturator unit for insertion through the skin portion of the mammal body and into a second of the lumens of the access device, and hub structure for supporting the first and second needle (or cannula) and obturator units, the hub structure comprising first and second hub bodies having the first and second needle (or cannula) and obturator units, respectively, fixed therein, (2) connecting the first needle (or cannula) and obturator unit to the second needle (or cannula) and obturator unit, (3) advancing the first and second needle (or cannula) and obturator units substantially simultaneously through the skin portion and into the first and second lumens, respectively, and (4) withdrawing needle portions of the first and second needle (or cannula) and obturator units to provide passageways between the access device and the hub bodies for flow of fluid therebetween.
The invention still further provides a method for accessing an access device disposed subcutaneously in a body of a mammal and having entrance lumens for transfer of fluid into and out of the mammal body, the method comprising the steps of (1) providing a needle (or cannula) and obturator assembly, the needle (or cannula) and obturator assembly comprising a first needle (or cannula) and obturator unit for insertion through a skin portion of the mammal body and into a first of the lumens of the access device, a second needle (or cannula) and obturator unit for insertion through the skin portion of the mammal body and into a second of the lumens of the access device, and hub structure for supporting the first and second needle (or cannula) and obturator units, the hub structure comprising first and second hub bodies having the first and second needle (or cannula) and obturator units, respectively, fixed therein, (2) advancing the first and second needle (or cannula) and obturator units individually through the skin portion and into the first and second lumens, respectively, (3) connecting the first needle (or cannula) and obturator unit to the second needle (or cannula) and obturator unit, and (4) withdrawing needle portions of the first and second needle (or cannula) and obturator units to provide passageways between the access device and the hub bodies for flow of fluid therebetween.
The invention still further provides a needle assembly comprising a needle having a distal end and a proximal end, the needle comprising a first lumen; a distal body element having a distal end and a proximal end, the distal end of the distal body element being mounted to the proximal end of the needle, and the distal body element comprising a second lumen, with the second lumen being in communication with the first lumen; a compressible tube having a distal end and a proximal end, the distal end of the compressible tube being mounted to the proximal end of the distal body element, and the compressible tube comprising a third lumen, with the third lumen being in communication with the second lumen; a proximal body element having a distal end and a proximal end, the distal end of the proximal body element being mounted to the proximal end of the compressible tube, and the proximal body element comprising a fourth lumen, with the fourth lumen being in communication with the third lumen; closure means connected to the compressible tube for selectively closing off the third lumen; and a cap having a distal end and a proximal end, the distal end of the cap being removably mounted to the proximal end of the proximal body element, and the cap comprising a fifth lumen, the fifth lumen being in communication with the fourth lumen when the cap is mounted to the proximal body element, and the cap comprising a septum extending transversely across the fifth lumen.
The invention still further provides a method for accessing the vascular system of a patient, the method comprising the steps of (1) providing a needle and obturator assembly comprising a needle having a distal end and a proximal end, the needle comprising a first lumen; a distal body element having a distal end and a proximal end, the distal end of the distal body element being mounted to the proximal end of the needle, and the distal body element comprising a second lumen, with the second lumen being in communication with the first lumen; a compressible tube having a distal end and a proximal end, the distal end of the compressible tube being mounted to the proximal end of the distal body element, and the compressible tube comprising a third lumen, with the third lumen being in communication with the second lumen; a proximal body element having a distal end and a proximal end, the distal end of the proximal body element being mounted to the proximal end of the compressible tube, and the proximal body element comprising a fourth lumen, with the fourth lumen being in communication with the third lumen; closure means connected to the compressible tube for selectively closing off the third lumen; a cap having a distal end and a proximal end, the distal end of the cap being removably mounted to the proximal end of the proximal body element, and the cap comprising a fifth lumen, the fifth lumen being in communication with the fourth lumen when the cap is mounted to the proximal body element, and the cap comprising a septum extending transversely across the fifth lumen; an obturator having a distal end and a proximal end, the obturator being removably disposed in the first lumen, the second lumen, the third lumen, the fourth lumen and the fifth lumen, with the obturator passing through the septum when the obturator is disposed in the fifth lumen; and locking means connected to the proximal end of the obturator for selectively locking the obturator to the cap; (2) passing the needle assembly through the skin of a patient so that the distal end of the needle is in communication with the vascular system of the patient; (3) unlocking the locking means; (4) removing the obturator from the first lumen, the second lumen, the third lumen, the fourth lumen and the fifth lumen; (5) engaging the closure means so as to close off the third lumen; (6) removing the cap from the proximal body element; and (7) disengaging the closure means so as to open up the third lumen; whereby access to the vascular system of the patient will be provided through the first, second, third and fourth lumens.